VATICAN CITY, Oct 6 (Reuters) - A Vatican court convicted Pope Benedict's former butler of stealing sensitive documents and sentenced him to 18 months in prison on Saturday, at the end of one of the most sensational trials in the recent history of the Holy See.

A Vatican spokesman said the pope, who reigns as a supreme monarch in the world's smallest city-state, would "most likely" pardon Paolo Gabriele, which would mean he would not have to serve his sentence.

The court delivered its verdict after two hours of deliberations and closing arguments by the prosecution and defence.

Gabriele had admitted being the source of leaks of highly sensitive papers, including letters to the pope that alleged corruption in the Vatican's business dealings.

"What I feel most strongly inside myself is the conviction that I acted exclusively out of love, I would say a visceral love, for the Church of Christ and its visible representative," he said in an impassive voice during a final appeal to the court.

"If I have to repeat it, I am not a thief," he added.

The prosecution had asked for a three-year sentence while the defence asked the court to reduce the charges from aggravated theft to misappropriation and for him to be freed.

The head of the three-judge panel, wearing a black robe with gold tassels, read the verdict with the opening words: "In the name of Holiness Pope Benedict XVI, gloriously reigning, the court has invoked the Holy Trinity and has reached its sentence."

The judge said he had given Gabriele a lighter sentence because he had no previous criminal record. The Vatican spokesman said the former butler had been returned to house arrest in the Vatican for the time being.

Gabriele's lawyer, Cristiana Arru, told Reuters she did not plan to appeal because she felt the sentence was "a just one".

"He is a serene man. He placed himself before justice and is ready to accept any of the consequences," she said after visiting the Gabriele family in their apartment in the Vatican.

"He put his life in the hands of divine providence first and human justice second. He is a man who has no fear," she said.

BREACH OF TRUST

The trial, which started last Saturday, threw open the window on a betrayal of trust and sensitive secrets in the Vatican.

A former member of the small, select group known as "the papal family", Gabriele was one of fewer than 10 people who had a key to an elevator leading directly to the pope's apartments.

In the course of the trial, intimate details emerged of the inner workings of an institution long renowned for its secrecy.

The documents Gabriele leaked constituted one of the biggest crises of Pope Benedict's papacy when they emerged in a muckraking expose by an Italian journalist earlier this year.

The case has been an embarrassment for the Vatican, coming at a time when it was keen to rid itself from the taint left by a series of scandals involving sexual abuse of minors by clerics around the world and mismanagement at its bank.

Gabriele told investigators before the trial began that he leaked the documents because he saw "evil and corruption everywhere in the Church" and that information was being hidden from the pope.

Earlier this week Gabriele accused the Holy See's police of mistreating him while in custody. Members of the force in turn depicted the butler as a man obsessed with the occult, Masonic lodges and secret services.